Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the orbiting scroll member via a suitable drive shaft.
Because scroll compressors depend upon successive chambers for suction, compression, and discharge processes, suction and discharge valves in general are not required. However, the performance of the compressor can be increased with the incorporation of a discharge valve. One of the factors which will determine the level of increased performance is the reduction of what is called recompression volume. The recompression volume is the volume of the discharge chamber and discharge port of the compressor when the discharge chamber is at its smallest volume. The minimization of this recompression volume will result in a maximizing of the performance of the compressor. In addition, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of a power interruption, there is a strong tendency for the backflow of compressed gas from the discharge chamber and to a lesser degree for the gas in the pressurized chambers to effect a reverse orbital movement of the orbiting scroll member and its associated drive shaft. This reverse movement often generates noise or rumble which may be considered objectionable and undesirable. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power interruption be experienced. This reverse operation may result in overheating of the compressor and/or other inconveniences to the utilization of the system. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the forward direction. However, the discharge pressure will again increase to a point where the drive motor is stalled and the cycle is repeated. Such cycling is undesirable in that it is self-perpetuating. The incorporation of a discharge valve can reduce or eliminate these reverse rotation problems.
A primary object of the present invention resides in the provision of a very simple and unique discharge valve which is associated with the non-orbiting scroll and which can easily be assembled into a conventional gas compressor of the scroll type without significant modification of the overall compressor design. The discharge valve operates to minimize the recompression volume and at compressor shut down operates to prohibit backflow of the discharge gas through the compressor and thus driving the compressor in the reverse direction. Prohibiting the reverse operation of the compressor eliminates the normal shut down noise and other problems associated with such reverse rotation. The discharge valve is normally open due to the configuration of the valve plate and the valve seat. The normally open configuration for the valve eliminates the force to open the valve as well as eliminating any mechanical device to close the valve. The valve relies on pressure differentials for closing. The stop plate for the discharge valve includes a curved backing surface which guides and supports the movement of the valve plate significantly reducing stresses for the valve plate. A second embodiment of the invention incorporates the unique discharge valve into a rotary vane compressor.
These and other features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.